/* 
 * $Header: /data/cvs/alin/nanhill-platform/src/main/java/org/nanhill/commons/dbutil/wrappers/SqlNullCheckedResultSet.java,v 1.1 2006/09/20 06:56:00 alin Exp $
 * $Revision: 1.1 $
 * $Date: 2006/09/20 06:56:00 $
 * 
 * ====================================================================
 * 
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.nanhill.commons.dbutil.wrappers;

import java.io.InputStream;
import java.io.Reader;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.net.URL;
import java.sql.Blob;
import java.sql.Clob;
import java.sql.Date;
import java.sql.Ref;
import java.sql.ResultSet;
import java.sql.Time;
import java.sql.Timestamp;
import java.util.HashMap;
import java.util.Map;

import org.nanhill.commons.dbutil.ProxyFactory;

/**
 * Decorates a <code>ResultSet</code> with checks for a SQL NULL value on each
 * <code>getXXX</code> method. If a column value obtained by a
 * <code>getXXX</code> method is not SQL NULL, the column value is returned.
 * If the column value is SQL null, an alternate value is returned. The
 * alternate value defaults to the Java <code>null</code> value, which can be
 * overridden for instances of the class.
 * 
 * <p>
 * Usage example: <blockquote>
 * 
 * <pre>
 *       Connection conn = // somehow get a connection
 *       Statement stmt = conn.createStatement();
 *       ResultSet rs = stmt.executeQuery(&quot;SELECT col1, col2 FROM table1&quot;);
 *       
 *       // Wrap the result set for SQL NULL checking
 *       SqlNullCheckedResultSet wrapper = new SqlNullCheckedResultSet(rs);
 *       wrapper.setNullString(&quot;---N/A---&quot;); // Set null string
 *       wrapper.setNullInt(-999); // Set null integer
 *       rs = ProxyFactory.instance().createResultSet(wrapper);
 *       
 *       while (rs.next()) {
 *           // If col1 is SQL NULL, value returned will be &quot;---N/A---&quot;
 *           String col1 = rs.getString(&quot;col1&quot;);
 *           // If col2 is SQL NULL, value returned will be -999
 *           int col2 = rs.getInt(&quot;col2&quot;);
 *       }
 *       rs.close();
 * </pre>
 * 
 * </blockquote>
 * </p>
 * 
 * @author <a href="stevencaswell@apache.org">Steven Caswell</a>
 * @author David Graham
 * @version $Id: SqlNullCheckedResultSet.java,v 1.1 2006/09/20 06:56:00 alin Exp $
 */
public class SqlNullCheckedResultSet implements InvocationHandler {

	/**
	 * Maps normal method names (ie. "getBigDecimal") to the corresponding null
	 * Method object (ie. getNullBigDecimal).
	 */
	private static final Map<String, Method> nullMethods = new HashMap<String, Method>();

	static {
		Method[] methods = SqlNullCheckedResultSet.class.getMethods();
		for (int i = 0; i < methods.length; i++) {
			String methodName = methods[i].getName();

			if (methodName.startsWith("getNull")) {
				String normalName = "get" + methodName.substring(7);
				nullMethods.put(normalName, methods[i]);
			}
		}
	}

	/**
	 * The factory to create proxies with.
	 */
	private static final ProxyFactory factory = ProxyFactory.instance();

	/**
	 * Wraps the <code>ResultSet</code> in an instance of this class. This is
	 * equivalent to:
	 * 
	 * <pre>
	 * ProxyFactory.instance().createResultSet(new SqlNullCheckedResultSet(rs));
	 * </pre>
	 * 
	 * @param rs
	 *            The <code>ResultSet</code> to wrap.
	 */
	public static ResultSet wrap(ResultSet rs) {
		return factory.createResultSet(new SqlNullCheckedResultSet(rs));
	}

	private InputStream nullAsciiStream = null;

	private BigDecimal nullBigDecimal = null;

	private InputStream nullBinaryStream = null;

	private Blob nullBlob = null;

	private boolean nullBoolean = false;

	private byte nullByte = 0;

	private byte[] nullBytes = null;

	private Reader nullCharacterStream = null;

	private Clob nullClob = null;

	private Date nullDate = null;

	private double nullDouble = 0.0;

	private float nullFloat = 0.0f;

	private int nullInt = 0;

	private long nullLong = 0;

	private Object nullObject = null;

	private Ref nullRef = null;

	private short nullShort = 0;

	private String nullString = null;

	private Time nullTime = null;

	private Timestamp nullTimestamp = null;

	private URL nullURL = null;

	/**
	 * The wrapped result.
	 */
	private final ResultSet rs;

	/**
	 * Constructs a new instance of <code>SqlNullCheckedResultSet</code> to
	 * wrap the specified <code>ResultSet</code>.
	 */
	public SqlNullCheckedResultSet(ResultSet rs) {
		super();
		this.rs = rs;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getAsciiStream</code> method.
	 * 
	 * @return the value
	 */
	public InputStream getNullAsciiStream() {
		return this.nullAsciiStream;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getBigDecimal</code> method.
	 * 
	 * @return the value
	 */
	public BigDecimal getNullBigDecimal() {
		return this.nullBigDecimal;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getBinaryStream</code> method.
	 * 
	 * @return the value
	 */
	public InputStream getNullBinaryStream() {
		return this.nullBinaryStream;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getBlob</code> method.
	 * 
	 * @return the value
	 */
	public Blob getNullBlob() {
		return this.nullBlob;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getBoolean</code> method.
	 * 
	 * @return the value
	 */
	public boolean getNullBoolean() {
		return this.nullBoolean;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getByte</code> method.
	 * 
	 * @return the value
	 */
	public byte getNullByte() {
		return this.nullByte;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getBytes</code> method.
	 * 
	 * @return the value
	 */
	public byte[] getNullBytes() {
		return this.nullBytes;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getCharacterStream</code> method.
	 * 
	 * @return the value
	 */
	public Reader getNullCharacterStream() {
		return this.nullCharacterStream;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getClob</code> method.
	 * 
	 * @return the value
	 */
	public Clob getNullClob() {
		return this.nullClob;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getDate</code> method.
	 * 
	 * @return the value
	 */
	public Date getNullDate() {
		return this.nullDate;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getDouble</code> method.
	 * 
	 * @return the value
	 */
	public double getNullDouble() {
		return this.nullDouble;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getFloat</code> method.
	 * 
	 * @return the value
	 */
	public float getNullFloat() {
		return this.nullFloat;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getInt</code> method.
	 * 
	 * @return the value
	 */
	public int getNullInt() {
		return this.nullInt;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getLong</code> method.
	 * 
	 * @return the value
	 */
	public long getNullLong() {
		return this.nullLong;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getObject</code> method.
	 * 
	 * @return the value
	 */
	public Object getNullObject() {
		return this.nullObject;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getRef</code> method.
	 * 
	 * @return the value
	 */
	public Ref getNullRef() {
		return this.nullRef;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getShort</code> method.
	 * 
	 * @return the value
	 */
	public short getNullShort() {
		return this.nullShort;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getString</code> method.
	 * 
	 * @return the value
	 */
	public String getNullString() {
		return this.nullString;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getTime</code> method.
	 * 
	 * @return the value
	 */
	public Time getNullTime() {
		return this.nullTime;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getTimestamp</code> method.
	 * 
	 * @return the value
	 */
	public Timestamp getNullTimestamp() {
		return this.nullTimestamp;
	}

	/**
	 * Returns the value when a SQL null is encountered as the result of
	 * invoking a <code>getURL</code> method.
	 * 
	 * @return the value
	 */
	public URL getNullURL() {
		return this.nullURL;
	}

	/**
	 * Intercepts calls to <code>get*</code> methods and calls the appropriate
	 * <code>getNull*</code> method if the <code>ResultSet</code> returned
	 * <code>null</code>.
	 * 
	 * @throws Throwable
	 * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object,
	 *      java.lang.reflect.Method, java.lang.Object[])
	 */
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {

		Object result = method.invoke(this.rs, args);

		Method nullMethod = (Method) nullMethods.get(method.getName());

		// Check nullMethod != null first so that we don't call wasNull()
		// before a true getter method was invoked on the ResultSet.
		return (nullMethod != null && this.rs.wasNull()) ? nullMethod.invoke(
				this) : result;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getAsciiStream</code> method.
	 * 
	 * @param nullAsciiStream
	 *            the value
	 */
	public void setNullAsciiStream(InputStream nullAsciiStream) {
		this.nullAsciiStream = nullAsciiStream;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getBigDecimal</code> method.
	 * 
	 * @param nullBigDecimal
	 *            the value
	 */
	public void setNullBigDecimal(BigDecimal nullBigDecimal) {
		this.nullBigDecimal = nullBigDecimal;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getBinaryStream</code> method.
	 * 
	 * @param nullBinaryStream
	 *            the value
	 */
	public void setNullBinaryStream(InputStream nullBinaryStream) {
		this.nullBinaryStream = nullBinaryStream;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getBlob</code> method.
	 * 
	 * @param nullBlob
	 *            the value
	 */
	public void setNullBlob(Blob nullBlob) {
		this.nullBlob = nullBlob;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getBoolean</code> method.
	 * 
	 * @param nullBoolean
	 *            the value
	 */
	public void setNullBoolean(boolean nullBoolean) {
		this.nullBoolean = nullBoolean;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getByte</code> method.
	 * 
	 * @param nullByte
	 *            the value
	 */
	public void setNullByte(byte nullByte) {
		this.nullByte = nullByte;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getBytes</code> method.
	 * 
	 * @param nullBytes
	 *            the value
	 */
	public void setNullBytes(byte[] nullBytes) {
		this.nullBytes = nullBytes;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getCharacterStream</code> method.
	 * 
	 * @param nullCharacterStream
	 *            the value
	 */
	public void setNullCharacterStream(Reader nullCharacterStream) {
		this.nullCharacterStream = nullCharacterStream;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getClob</code> method.
	 * 
	 * @param nullClob
	 *            the value
	 */
	public void setNullClob(Clob nullClob) {
		this.nullClob = nullClob;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getDate</code> method.
	 * 
	 * @param nullDate
	 *            the value
	 */
	public void setNullDate(Date nullDate) {
		this.nullDate = nullDate;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getDouble</code> method.
	 * 
	 * @param nullDouble
	 *            the value
	 */
	public void setNullDouble(double nullDouble) {
		this.nullDouble = nullDouble;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getFloat</code> method.
	 * 
	 * @param nullFloat
	 *            the value
	 */
	public void setNullFloat(float nullFloat) {
		this.nullFloat = nullFloat;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getInt</code> method.
	 * 
	 * @param nullInt
	 *            the value
	 */
	public void setNullInt(int nullInt) {
		this.nullInt = nullInt;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getLong</code> method.
	 * 
	 * @param nullLong
	 *            the value
	 */
	public void setNullLong(long nullLong) {
		this.nullLong = nullLong;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getObject</code> method.
	 * 
	 * @param nullObject
	 *            the value
	 */
	public void setNullObject(Object nullObject) {
		this.nullObject = nullObject;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getRef</code> method.
	 * 
	 * @param nullRef
	 *            the value
	 */
	public void setNullRef(Ref nullRef) {
		this.nullRef = nullRef;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getShort</code> method.
	 * 
	 * @param nullShort
	 *            the value
	 */
	public void setNullShort(short nullShort) {
		this.nullShort = nullShort;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getString</code> method.
	 * 
	 * @param nullString
	 *            the value
	 */
	public void setNullString(String nullString) {
		this.nullString = nullString;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getTime</code> method.
	 * 
	 * @param nullTime
	 *            the value
	 */
	public void setNullTime(Time nullTime) {
		this.nullTime = nullTime;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getTimestamp</code> method.
	 * 
	 * @param nullTimestamp
	 *            the value
	 */
	public void setNullTimestamp(Timestamp nullTimestamp) {
		this.nullTimestamp = nullTimestamp;
	}

	/**
	 * Sets the value to return when a SQL null is encountered as the result of
	 * invoking a <code>getURL</code> method.
	 * 
	 * @param nullURL
	 *            the value
	 */
	public void setNullURL(URL nullURL) {
		this.nullURL = nullURL;
	}

}
